Unfortunately last week featured a complete absence of swimming of any sort. Even though I was never more than a few feet from water, a swim would have been easy to instigate but challenging to conclude because I’ve spent the week as a watch leader on board Tall Ship Stavros S Niarchos, a 148ft traditionally rigged brig with a long drop to the sea. Over the week we sailed round the isle of Arran renowned for its diverse geology and scenery and as a geologist this was a bit of a busman’s holiday. As I don’t have any swimming tales to tell I thought I’d look at the geology of the swim course instead.
The Thames used to be a lot bigger and flow to the north through Suffolk/Norfolk before joining the Rhine in a now submerged area of the North Sea. When the last set of Ice Ages occurred, the ice front blocked the path of the Thames and diverted it south along its current course. So if we were swimming the mile along a historic section of the mid-Thames we may well have been splashing through Northamptonshire instead.
Over centuries of flowing through its current course silt, sand and mud has been carried downstream building up an area of flat floodplain around the river, this is what the river bed is made of and why the water is so murky to swim in. Underneath the floodplain lies chalk, a rock made from the bodies of microscopic sea creatures during the Cretaceous – a time when many dinosaurs roamed the earth.
Fortunately the water is now free of toothy prehistoric creatures and the swim can take place amongst the green chalk hills instead.
I plan to do lots more swimming this week to compensate for the break in training last week, I’ve found a swim fit class that does drills (I thought I was ok in the water until attempting butterfly) and may even chance my first open water swim. Or open water dunk. Maybe.